Good news for older women who have used oral contraceptives in the past — according to a study reported in the June 27 New England Journal of Medicine (NEJM, Vol. 346, No. 26: 2025-2032) there is no evidence that oral contraceptive use increases breast cancer risk.

Study author Polly A. Marchbanks, PhD, and colleagues from centers around the US, questioned a report published in 1996. That report analyzed 54 studies that had been conducted over the last 25 years. It found that past use of oral contraceptives increased a woman's risk of developing breast cancer.

Researchers in the NEJM study interviewed more than 9,000 women with and without breast cancer. They included women age 35 to 64, since the risk of breast cancer increases as a woman gets older.

The interviewers didn't just ask about oral contraceptive use. They also asked the women questions about their education, income, exercise habits, alcohol use, and smoking histories.

Despite looking at a number of different conditions that might affect breast cancer risk, including age, race, type of oral contraceptives, and many others, the authors could find no evidence that oral contraceptives had any effect on increasing the risk of breast cancer.

Even women at increased risk of breast cancer because of family history did not have any additional increased risk if they used, or had used, oral contraceptives.

This study did not specifically look at the question for women known to have either BRCA1 or BRCA2 mutations, which are associated with increased risk of breast and ovarian cancers. It only asked about family history of breast cancer, not whether testing for the BRCA genes had been done.

Other studies have shown that oral contraceptives increase the already high risk of breast cancer in women with these mutations, according to the authors.

In an editorial in the same issue of the NEJM (2078-2079), Nancy E. Davidson, MD, and Kathy J. Helzlsouer, MD, MHS, from Johns Hopkins Medical Institutions in Baltimore praised the study.

"The importance of this finding for public health is enormous, because more than 75% of the women in the study had used oral contraceptives. No subgroup of women who used oral contraceptives had a significantly increased risk of breast cancer. On the whole, …the results of this study should be reassuring to the millions of women who take oral contraceptives," they wrote.

But, the doctors noted, there are some risks for women who take oral contraceptives. This is especially true for women over 35 years of age who smoke and therefore have a greater chance of a heart attack if they use oral contraceptives. But, they said, the benefits of oral contraceptives clearly outweigh the risks.

Davidson and Helzlsouer said, "Attention should shift from concern about the possible adverse effects of current oral contraceptives to the identification of an ideal oral contraceptive, one that would reduce the risk of breast, ovarian, and uterine cancer without cardiovascular (heart and blood vessel) complications."